Match the tag page row hover to the rest of the site

[ryanportfolio]

The tag pages had their own flat hover: a hard-edged blue rectangle that ran the full width of the row. Every other shelf row on the site (track pages, homepage tracks) uses the feathered treatment instead.

This ports that treatment onto the tag page shelf rows, matching src/pages/tracks/[slug].astro line for line:

• wash gradient that fades out at the left and right edges instead of stopping in a rectangle
• dashed accent line that draws itself along the row divider
• the star that ignites next to the guide number
• title underline that grows in, plus the accent glow on title and meta

Same markup, same class names, so nothing else changed. Build passes; browser check was declined, so the hover was not visually confirmed in a running preview.